1. Field of the Invention
The present invention relates to an attachment jig and a gauge inspection machine used to inspect a gauge. Specifically, the present invention relates to a jig and gauge inspection machine inspecting metrological characteristics of a gauge (such as a dial gauge) in an inverted posture, where a stylus head points upward, when inspecting the gauge.
2. Description of Related Art
A dial gauge is known as an example of a type of comparator. Dial gauges include a spindle-type and a lever-type. FIG. 14 illustrates a spindle-type dial gauge 10. A simplified description of dial gauges follows, with reference to FIG. 14.
The dial gauge 10 includes a cylindrical casing 11, a spindle 15 which is capable of displacing vertically, and a stem 20 projecting from the casing 11. A dial face (display) 12 is provided on a front surface of the casing 11. A gear mechanism (not shown in the drawings) is provided on an interior of the casing 11, the gear mechanism magnifying a displacement of the spindle 15 and transmitting the change to a pointer 13. A stylus head 16 is provided to a bottom end of the spindle 15. The stem 20 slidably supports the spindle 15.
The spindle 15 is inserted through the casing 11, and a top end of the spindle 15 projects from the casing 11. Then, in order to protect the top end portion of the spindle 15, a cap 21 is provided on a lateral surface of the casing 11. FIG. 15 illustrates a state where the cap 21 is separated from the casing 11. A hole, through which the top end portion of the spindle 15 projects, is bored into the lateral surface of the casing 11 (not shown in FIG. 15), and a hollow male threading portion 14 is provided to a circumference of the hole. The cap 21 can be screwed onto the male threading portion 14.
In addition, a stopper screw 18 can be threaded into the top end portion of the spindle 15. The stopper screw 18 includes a flange 19 which flares out from the stopper screw 18. The flange 19 is a stopper for the spindle 15 due to abutting an edge of the hole (more accurately, the edge of the male threading portion 14). The cap 21 is designed with a sufficient inner diameter and depth to allow the stopper screw 18 to move vertically.
In this connection, dial gauge performance is regulated in ISO 463 (http://wvvw.iso.org/iso/home/store/catalogue_ics/catalogue_detail_ics.htm?csnumber=42802) and JISB 7503 (http://kikakurui.com/b7/B7503-2011-01.html). Manufacturers of dial gauges must inspect their products to determine whether the dial gauges satisfy regulation values as stipulated in ISO 463 and JISB 7503. When inspecting dial gauges, indication accuracy, measurement force, and repetition accuracy must be inspected.
Inspecting dial gauges involves a large number of measurement instances, and must be performed repeatedly, which requires a great deal of time and effort. Given this, Applicant (a manufacturer of dial gauges) has already developed gauge inspection machines to enable inspection of dial gauges to be performed efficiently and easily according to a determined inspection rubric (for example, Japanese Patent Laid-open Publication No. H04-31531, Japanese Patent No. 2,645,576, Japanese Patent Laid-open Publication No. 2002-122402, and Japanese Patent Laid-open Publication No. 2002-122404). A simplified summary description of known gauge inspection machines follows. An exterior view of a gauge inspection machine is shown in FIG. 16, and an interior configuration of a gauge inspection machine is shown in FIG. 18. FIG. 17 shows a state where a dial gauge has been arranged on the gauge inspection machine. A gauge inspection machine 100 includes a bracket 110 which securely holds the dial gauge 10. The bracket 110 securely holds the dial gauge 10 by pinching the stem 20 of the dial gauge 10. The dial gauge 10 may come in a variety of sizes, and therefore the bracket 110 is provided so as to be freely raised and lowered so as to change a height position. Specifically, a backboard 120 having a guide rail 121 stands upright on a casing 130, and the bracket 110 can be freely raised and lowered along the guide rail 121. In addition, the bracket 110 can be fixed in a position by operating a handle 111.
The gauge inspection machine 100 includes a measurement spindle 140 provided so as to be capable of advancing and retreating in a vertical direction. As shown in the internal structure depicted in FIG. 18, a motor 131 and a ball screw 132 are installed inside the casing 130. The ball screw 132 advances and retreats in the vertical direction due to drive power of the motor 131. Specifically, the motor drive power turns and stops the ball screw 132, and rotates a nut 133. Accordingly, the ball screw 132 advances and retreats. An amount of advance/retreat of the ball screw 132 can be precisely detected by an encoder 134. A scale of the encoder 134 is provided parallel to the ball screw 132, and a detection head is fixated to the ball screw 132. In addition, a flat stylus head 141 can be threaded into a top end portion of the measurement spindle 140.
An exemplary protocol is introduced in which inspection of the dial gauge 10 is performed using the gauge inspection machine 100. (Please see FIG. 19.) The protocol is intended to inspect how much a measured value shown by the dial gauge 10 differs from a true value. The gauge inspection machine 100 automatically raises the measurement spindle 140 to a point just shy of around 20 mm. From this point, an inspector manually raises the measurement spindle 140, displacing the measurement spindle 140 until the pointer 13 points at 20 mm. (Fine adjustment of the measurement spindle 140 can be performed with a switch 151 or jog dial 152 on a console 150.) A position of the measurement spindle 140 at this time is measured by the encoder 134. The measured value of the encoder 134 is captured and recorded on a computer 160.
The same operation is performed to 30 mm, 40 mm, and so on, and indication accuracy throughout the entire measurement range of the dial gauge 10 is measured. Moreover, in order to determine repetition accuracy, the same protocol is repeated a predetermined number of times throughout the entire measurement range of the dial gauge 10.
The gauge inspection machine 100 can automatically raise and lower the measurement spindle 140, and can precisely measure the amount of displacement of the measurement spindle 140. Therefore, inspection of the dial gauge 10 is understood to be simple and efficient when using the gauge inspection machine 100.
ISO 463 was revised in 2006, and JISB 7503 was revised in 2011. The following was added by way of these revisions. “Metrological characteristics where not indicated by a manufacturer must meet values for MPE and MPL at all positions within a measurement range, in all orientations.” A maximum permissible error (MPE) of a dial gauge is a maximum value of an indication error allowed for an indicated value. A permissible limit (MPL) is a threshold value of measurement force permissible by specification for measurement force.
According to this revision, a scenario may arise requiring inspection as to whether a regulation value is met even in an orientation other than the typical downward pointing posture of the stylus head. A representative example may be imagined of a scenario where a user desires the ability to take a measurement even in an orientation other than the downward pointing posture of the stylus head, for example. Accordingly, manufacturers require a strategy to enable inspection of a dial gauge even in an orientation other than the downward pointing posture of the stylus head.